The present invention relates to man holes and more particularly to mounting and locking of man hole covers in frames surrounding the man holes.
There are known man holes formed of a frame on which is mounted a cover which is closed on the frame by screws. These screws are usually but not necessarily projections integral with the cover acting on inclined members of the frame, rotation of the cover in the closing direction having as its effect the bringing together of the cover and the frame and formation of a connection between the two.
It is desirable for covers of this type, and generally in all cases where the cover is movable in rotation with respect to the frame, to provide a device for locking the cover in a given position.
In the case of covers which are closed by rotation, such locking is particularly desirable in that it allows the cover to be maintained closed and thus avoids any rotation in the opening direction which might be caused by vibrations and repeated passage of vehicles. Such locking is especially important in the case of covers intended for roads which have to bear large numbers of heavy loads.
It is also desirable to prevent the locking means from causing the surface of the road, which includes the cover when in position, to have roughness or cavities which may be dangerous for traffic and may have bad effects on the tires of vehicles.